ESTRO 2020 Abstract book

S613 ESTRO 2020

room for re-irradiation for intrahepatic out-field failure. PO-1069 SBRT in Hepatocellular Carcinoma: impact of dose regimen and treatment sequence M. Loi 1 , T. Comito 1 , C. Franzese 1 , E. Clerici 1 , M. Badalamenti 1 , G. Reggiori 1 , P. Mancosu 1 , S. Tomatis 1 , L. Rimassa 2 , A. Santoro 2 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy, Rozzano, Italy ; 2 Istituto Clinico Humanitas, Medical Oncology, Rozzano, Italy Purpose or Objective Standard management of Hepatocellular Carcinoma (HCC) includes surgery , trans-catheter arterial chemoembolization (TACE), radiofrequency ablation (RFA), percutaneous ethanol injection (PEI), or systemic therapies. Stereotactic body radiotherapy (SBRT) recently emerged as an option in HCC patients ineligible for standard local therapies or following incomplete response after primary treatment. However, the benefit of this strategy, its role in the treatment sequence and the appropriate dose regimen is debated. The aim of this study is to evaluate outcome and predictors of response to treatment in a retrospective HCC cohort treated with SBRT. Material and Methods Clinical and treatment-related data from HCC patients treated with SBRT at our institution between January 2011 and September 2017 were retrospectively reviewed. Biological Effective Dose (BED) was calculated to compare different dose regiments. Local control (LC), Progression- Free Survival (PFS) and Overall Survival (OS) at 1 and 2 years were calculated using the Kaplan-Meier method. Toxicity was scored using the Common Terminology Criteria for Adverse Events (CTCAE) v.4.03. Univariate and multivariate analysis was performed to assess the impact of clinical and treatment-related variables on outcome. Results One-hundred-seventeen HCC patients were included, classed according to Barcelona staging (BCLC) system in A, B and C in respectively 39 (33%), 64 (55%) and 14 (12%) cases . Median age was 75 (range 45-88) years. Eighty- seven patients (78%) had received prior liver-directed treatments consisting of surgery, RFA, PEI or TACE in 20 (17%), 18 (15%), 38 (32%) and 59 (50%) cases respectively. SBRT was delivered to a median dose of 54 (range 30-78) Gy in 6 (range 3-10) fractions, corresponding to a median BED of 120 (range 56-263) Gy 10 . Median cumulative gross tumor volume (GTV) size was 40 (range 8-116) cc. One- year LC rate was 82% (CI95%:72-89). Among the examined variable (age, etiology, BCLC, thrombosis, multiple foci, prior treatment, cumulative GTV size, BED) only BED ≥120 Gy 10 was correlated to improved LC (median not reached, p= 0.0046). One-year PFS was 41% (CI95%:32-51) with intrahepatic failure as the dominant pattern of primary recurrence in 45% (n=57) of patients: no variable was associated to a poorer PFS. One-year OS was 82% (CI95%:70-90): only prior surgery was correlated to improved survival (median 29 versus 17 months, p=0.036). Overall toxicity was reported in 15% (n=18) of patients. Grade 3 toxicity was reported in 2 cases, consisting of transient acute liver failure.

versus 18 months; p= 0.04). Local failures were documented in 75% (80) patients of which 37% (30) had failure. Distant failures were documented in 82% (87) of which 28% (30) had distant disease. Local (p=0.02) and distant failure (p=0.03) were significantly lower in complete responders. 27 (26%) patients had >10% weight loss of the usual body weight in the preceding 6 months. 36% of the total cohort planned for surgery did not undergo Esophagectomy. Our retrospective analysis showed a pathological complete response rate of 29.4%, and these had statistically significant superior OS and lower relapse rates. Conclusion We concluded that neo adjuvant chemo-radiotherapy improves pathological complete response and and eventually improves the overall survival. It should be the standard approach in treating resectable esophageal carcinoma patients. PO-1068 How much lower dose is enough for SBRT in hepatocellular carcinoma considering normal liver? T. Nam 1 , J. Jae-Uk 1 , S. Ju-Young 1 , Y. Mee Sun 1 , A. Sung- Ja 1 , C. Woong-Ki 1 , C. Ick Joon 1 , K. Yong-Hyub 1 , C. Shin Haeng 1 1 Chonnam National University Hwasun Hospital, Radiation Oncology, Hwasun-gun Jeonnam-, Korea Republic of Purpose or Objective To determine adequate total dose for not only tumor control but also maximizing remnant normal liver volume in stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) Material and Methods SBRT was performed in 62 HCC patients with a total dose of 20 ~ 60 Gy in one to four fractions (median: 48 Gy, 4 fractions) in respiratory gating mode. Biologically equivalent dose in α/β = 10 Gy (BED 10 ) of prescribed total dose had a wide range of 38 ~ 180 Gy (median: 109). Gross tumor volume (GTV) was 1 ~ 274 mL (median: 10.6) and planning target volume (PTV) was 14 ~ 385 mL (median: 41.0). Normal liver volume (NLV: whole liver volume minus GTV) was 639 ~ 1928 mL (median: 1219). We planned rV15 (NLV receiving less than 15 Gy in 3 fractions) or rV17 (NLV receiving less than 17 Gy in 4 fractions) to be at least 700 mL. In-field failure-free survival (IFFS), progression-free survival (PFS), and overall survival (OS) were calculated. We collected data of BED 10 according to the GTV, PTV, GTV/NLV (percent of GTV to NLV), and PTV/NLV (percent of PTV to NLV) among in-field failure-free patients. Results Follow-up time was 3 ~ 46 months (median: 14) in all patients. One-year IFFS, PFS, and OS were 87.4%, 40.4%, and 88.2%, respectively. Including combined failures, in- field failure occurred in 11 patients (17.7%), intrahepatic out-field failure in 34 (54.8%), extrahepatic failure occurred in 13 (21.0%). No patient developed hepatic toxicity. BED 10 , GTV, and PTV were not significantly different between in-field control and in-field failure groups. Among 51 patients with in-field control, Mean BED 10 was not significantly different according to the GTV (113.0 vs. 110.4 Gy in ≤ 10 vs. > 10 mL), PTV (112.3 vs. 110.9 Gy in ≤ 40 vs. > 40 mL), GTV/NLV (117.4 vs. 104.5 Gy in ≤ 1 vs. > 1), and PTV/NLV (123.2 vs. 102.2 Gy in ≤ 3 vs. > 3). Meanwhile, V15 or V17 was significantly correlated with GTV ( p =0.000, R 2 =0.428), PTV ( p =0.000, R 2 =0.379), GTV/NLV ( p =0.000, R 2 =0.422) , and PTV/NLV ( p =0.000, R 2 =0.382). Conclusion We found no BED 10 differences according to GTV or PTV, and its relative volume to NLV in in-field control group. However, the larger the GTV or PTV, the V15 or V17 also increased. We suggest that as low as 100 Gy of BED 10 could be adequate dose for tumor control and also for sparing much more remnant normal liver, which might provide a